Er. UV maps can and are allowed to overlap, as far as I know.
When you pull default texture maps out of UV maps, you can limit which ones you want to display, save them, and move to a new section.
That only works if they are different mat zones or groups. Here the same zones and body part groups are overlaid. So if you make a texture the mapping will have no idea which part it belongs to.
I’ve put in a ticket with description and the images so it will get fixed eventually.